We present Gemini and Keck spectroscopic redshifts and velocity dispersions for twenty clusters detected via the Sunyaev-Zel ’ dovich ( SZ ) effect by the Planck space mission , with estimated masses in the range 2.3 \times 10 ^ { 14 } M _ { \odot } < M ^ { \text { Pl } } _ { 500 } < 9.4 \times 10 ^ { 14 } M _ { \odot } .
Cluster members were selected for spectroscopic follow-up with Palomar , Gemini and Keck optical and ( in some cases ) infrared imaging .
Seven cluster redshifts were measured for the first time with this observing campaign , including one of the most distant Planck clusters confirmed to date , at z = 0.782 \pm 0.010 , PSZ2 G085.95+25.23 .
The spectroscopic redshift catalogs of members of each confirmed cluster are included as on-line tables .
We show the galaxy redshift distributions and measure the cluster velocity dispersions .
The cluster velocity dispersions obtained in this paper were used in a companion paper to measure the Planck mass bias and to constrain the cluster velocity bias .